Friday, November 28, 2008

Something about "NISHA" from Jim's blog, www.accuweather.comThanks to some "fancy footwork", the center of Tropical Cyclone Nisha held offshore for something like another 10 or 12 hours following its earlier purported landfall. While satellite imagery seemed to confirm the earlier time, surface winds and pressure field belied it. I note here that slowly moving tropical cyclones will often tend to keep a center over water until the whole mass is committed to shift inland. Anyways, there is no doubt that, as of 1800 UTC, Thursday, the center of Nisha is inland and dissipating. Wind and tide are thus no longer a big factor; however, satellite imagery makes it clear that torrential downpours are still taking place. One has poured 10 cm of rain upon Cuddalore within three hours. This hikes to 68 cm/26.8 inches the rainfall here since late last week (5 to 6 days). Readers may wish to browse comments from the foregoing post. Here is one segment relating to torrential rain and widespread severe flooding:

"The following stations recorded extremely heavy rainfall in centimetres:Orathanadu (Thanjavur dt) 66, Thanjavur 53, Vedaranyam 42, Adiramapattinam 33, Muthupet (Tiruvarur dt) 30 and Kumbakonam (Thanjavur dt) 26."I have never seen a 24-hr rainfall total of 66 cm anywhere in Tamil Nadu. Simply unbelievable. Chennai's 24-hr rainfall was 14 cm. Needless to say, widespread flooding and devastation of winter crops, especially in the Thanjavur-Thiruvarur-Nagapattinam belt (the so-called 'rice bowl' of South India), off where the storm hovered for 2 days before landfall.Looking forward, the old core of Nisha will drift northwest during the next few days, which means it will leave land for the eastern Arabian Sea. Showers and downpours will fade over coastal southeast India even as the leading edge of showers and thunderstorms shifts north and west to Karnataka and Maharashtra. There is even the believable scenario of scattered showers and thunderstorms reaching Gujarat and southermost Sindh, Pakistan. One thing to raise before leaving South Asia: strong north-south pressure gradient will stir up strong easterly winds along and right down wind of the crest of the Western Ghats in Maharashtra and Karnataka through Friday night, local time. Oh, and still another thing. Recall that, as of the start of the week, I was speaking about another tropical cyclone "threat". Well, I will now say the we have had the cyclone--in the shape of TC Nisha, which proved to "steal the show". -----------------------------------------------Well, not only did Tuesday's tropical depression get upgraded to tropical cyclone, it became a rather strong tropical storm before its landfall upon southeastern India between 0600 UTC and 1200 UTC, Wednesday. Shortly before landfall, Tropical Cyclone Nisha was reckoned, by the JTWC, to have highest sustained winds of 55 knots/100 km/h. Landfall happened over the state of Tamil Nadu between Karaikal (Puducherry) and Vedaranniyam. Thus, the time between upgrade over northern Sri Lanka and landfall in India was between 12 and 18 hours. While there potentially damaging winds near the landfall of Nisha (gales observed at Karaikal as of 0900 UTC), the storm, both before and after its upgrade, was, foremost of all, a rainmaker. In northern Sri Lanka, a report of about 24 inches/60 cm of rain within two to three days at Jaffna seems believable. In southeast India, where the North East Monsoon has been stirring up local heavy rain for several days, rainfall has reached at least 21.9 inches/55.6 cm at Cuddalore, Tamil Nadu, and 16.4 inches/41.7 at Karaikal, Puducherry, as of 1800 UTC--and still falling. This is serious flooding rainfall. And at Chennai, rainfall since late last week is at least 10.5 inches/26.7 cm. For Chennai, this brings November rainfall to near normal. Nisha will dissipate within about 24 hours over the southern Deccan of India. But there will be showers and thunderstorms with local heavy falls over Tamil Nadu and Andhra Pradesh with significant, if spotty, rain into Kerala and Karnataka. And, if the latest (1200 UTC, Wednesday) GFS forecast scenario hold true, this weekend into early next week will see scattered showers and thunderstorms spreading not only over western Maharashtra, but into Gujarat and even southern Sindh, Pakistan.

"Nisha's" cloud mass crossed over Chennai before moving into South-Andhra.Now(12:30PM) the cloud mass is in South-Andhra.See for urself...Chennai received around 50 CM in last 4 days...City infrastructure does not support this kind of bursts.We received abnormally heavy showers thru the day yesterday (27-Nov-08) and night till Early morning of 28-Nov-08.After that we had SUN for a while, then we are experiencing some mild showers.All roads are like RIVERS and LAKES.These mild showers are making it even more worse.Chennai was receiving showers from East-south-east yesterday , now receiving from South-south-east.Most parts of CHENNAI are still without electricity.We are expecting more disaster videos & Photos to pop up in YOUTUBE & FLICKR.Meanwhile numeric models show a NEW cyclone around 2-Dec-08.